Atheism Impossible to Argue Against?

In a formal argument, the opponent brings an objection to the proponent's position. Theists make the assertion there is a God, while Atheists make the opposite assertion. In this case, the theist is the proponent for the existence of God and the Atheist is opposed to this position for various reasons.


Yet what if the theist, or religious adherent, wishes to criticize the nonbeliever's position? I find this a horribly impossible task--because to claim the atheist is wrong the theist would first be required to validate their position that God exists. In other words, they would have to present us with God (exhibit A). Oddly, exhibit A seems to be missing. How can a theist presume to claim the atheist is wrong about the non-existence of exhibit A when the theist can't even provide physical evidence and, perhaps more importantly, any reliable evidence seems so elusive (illusive)?


Personally I find it amusing that theists would even try to argue against the atheistic position. Usually when an argument is made, the argument it is brought with evidence to justify the claims. After all, the goal is to prove the other side wrong. 


But how does one go about proving something someone doesn't believe in is (somehow) incorrect? Moreover, how does the theist propose to support their claim that the atheist is mistaken about the non-existent status of God when they can't even provide trustworthy, testable, falsifiable evidence for God? 


It seems a futile position, at least to me, to argue that somebody is mistaken without the evidence to prove why (or how) they are mistaken all the while realizing that you aren't actually disproving a belief--but rather trying to argue against a position which is, strangely enough, a statement of what one doesn't profess to believe. It is unreasonable to make a claim that someone else is mistaken then completely fail to provide a proper basis for that claim to be checked against. Yet this is the very thing which theists are doing when they attack atheism.


Sure, atheists may turn out to be gravely mistaken, but there is just no way to prove it. Not without the prerequisite verification of evidence and either the proof or falsification of the disputed claims. Meanwhile, atheists aren't under any particular obligation to disprove God, because minus the evidence for God, their claim that there is nothing to disprove happens to fall in line with the observable facts.

Therefore the burden is forever on the theist to provide valid evidence. Until then, their claims are without basis and without merit. For this very reason, it seems to me, atheism is an impossible position to argue against.